Ultra-Wideband (UWB) technology is a wireless technology for the transmission of digital data as modulated coded impulses over a very wide frequency spectrum with very low power over a short distance. Such pulse based transmissions are an alternative to transmitting information using a modulated sinusoidal wave, which is the technique currently employed within today's wireless communication standards and systems such as IEEE 802.11 (Wi-Fi), IEEE 802.15 wireless personal area networks (PANs), IEEE 802.16 (WiMAX), Universal Mobile Telecommunications System (UMTS), Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), and those accessing the Industrial, Scientific and Medical (ISM) bands, and International Mobile Telecommunications-2000 (IMT-2000).
UWB transmission from an antenna is defined by an emitted signal bandwidth that exceeds the lesser of 500 MHz or 20% of the center frequency. Thus, pulse-based systems where each transmitted pulse occupies the full UWB bandwidth or an aggregate of at least 500 MHz of narrow-band carriers; for example, orthogonal frequency-division multiplexing (OFDM); can gain access to the UWB spectrum under the rules. Pulse repetition rates may be either low or very high. Pulse-based UWB radars and imaging systems tend to use low to moderate repetition rates (typically in the range of 1 to 100 megapulses per second). On the other hand, communications systems favor high repetition rates (typically in the range of one to two gigapulses per second), thus enabling short-range gigabit-per-second communications systems. As each pulse in a pulse-based UWB system occupies a large bandwidth, possibly even the entire UWB bandwidth, such systems are relatively immune to multipath fading but not intersymbol interference, unlike carrier modulation based systems which are subject to both deep fading and intersymbol interference (ISI).
When considering applications, such as wireless sensor networks and portable electronics, UWB transceivers should ideally be functionally highly integrated for small footprint, support low cost and high volume manufacturing, and be energy efficient in order to run on a limited power source, e.g. a battery, indoor solar cell, small outdoor solar cell, or those developed upon evolving technologies such as thermal gradients, fluid flow, small fuel cells, piezoelectric energy harvesters, micro-machined batteries, and power over optical fiber. By using discrete pulses as modulation, it is possible to implement efficient duty cycling schemes while the transmitter is not active, which can be further improved by using an On-Off Shift Keying (OOK) modulation.
Further, some UWB operation frequencies, between 3.1 GHz and 10.6 GHz for example, are approved by Federal Communications Committee for indoor UWB communication systems and allow for small antennas which can easily be integrated into overall reduced footprint solutions such as sensors, mobile devices or portable electronics etc. Accordingly, UWB systems with low power consumption can support a wide range of applications including, but not limited to, sensor networks, smart buildings, medical devices, remote sensing, remote monitoring, remote controls, agriculture, industrial, control, automation, personal monitoring, etc.
Such UWB systems through their receivers may also operate in the presence of interfering signals providing for robust communications within noisy wireless environments and unregulated wireless environments. Accordingly, it would be beneficial to provide circuit designers with an accurate and sharp filter that operates at low power. The inventors present such as filtering methodology that removes the requirement for an accurate carrier wave within the receiver.
Within many of the applications for UWB devices the location and/or range finding of other elements with precision is a desirable or obligatory requirement. Accordingly, it would be beneficial to provide circuit, device and system designers with a UWB based range finding and/or location capability removing the requirement to add additional complexity and, typically significant, power consumption by adding global positioning system (GPS) receiver(s) or ultrasonic/laser range finding circuits and/or devices. It would be further beneficial for such UWB based location and/or range finding applications to maintain the overall low power consumption of the UWB impulse radios.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.